question_answer

A rod PQ of mass M and length L is hinged at end  P. The rod is kept horizontal by a massless string tied to point Q as shown in the figure. When string is cut, the initial angular acceleration of the rod is

A) \[\frac{3g}{2L}\]

B) \[\frac{g}{L}\]

C)  \[\frac{2g}{L}\]

D)  \[\frac{2g}{3L}\]

Correct Answer: A

Solution :

 Taking torque about P \[Mg=\frac{L}{2}=\left( \frac{M{{L}^{2}}}{3} \right)\alpha \] Hence \[\alpha =\frac{3g}{2L}\]